In the US ‘silver steel’ is called tool steel in flats & drill
rod in rounds.
Drill rod is available in many diameters usually 36 inches long.
Flats come in many thicknesses & widths, usually 18 or 36 inches
long. Generally you can get it in 3 different varieties, oil
water, or air hardening, oil hardening is most common. It’s all
alloyed for hardening to cut ferrous & non ferrous metals. The
dimensions of the material as it comes from the supplier is very
accurate, within +/- .001inch.
It’s usually available at any industrial supply house.